The present invention relates to the area of injection molding and in particular to valve pin actuators for runnerless injection molding systems, often referred to as hot runner systems. In runnerless valve gated systems for use in plastic injection molding industry, actuators are used to provide linear movement of the valve pins. The actuators pull the valve pin open prior to the start of injection allowing the plastic to flow from the injection molding machine through the runnerless system into the mold cavity. At the completion of the filling process the actuator closes valve pin preventing drooling of material when injection mold opens and plastic part is removed from the injection mold.
The actuator can be controlled hydraulically, pneumatically or electrically.
The valve pin is considered a wear item as well as the seals contained in the actuator assembly and the actuator assembly itself. These items periodically require maintenance or replacement. The valve pin contained in the actuator assembly are located typically within the top clamp plate of the injection mold runnerless system. Access to the valve pin usually requires some type of disassembly of the injection mold to gain access to actuator assembly where the valve pin is housed or attached. Access to the valve pin, typically housed within the actuator assembly, can be time consuming and difficult, requiring substantial disassembly of the injection mold gain access to the actuator assembly and the valve pin contained in the actuator assembly. In the case of hydraulic actuators, the disassembly process can be messy with hydraulic fluid leaking during disassembly. Current designs don't allow for removal of actuator assembly independent of the valve pin. In conjunction present designs don't allow removal of valve pin independent of the actuator assembly.
Ease of access to the valve pin and actuator assembly as in current designs is difficult and problematic. Because of the current designs constraints, access to the valve pin and assembly in some cases requires heating the runnerless system in order to remove the valve pin and actuator assembly in order to get to the internal components of the runnerless system. The valve pin is disposed within the runnerless system and is typically surrounded by plastics material. If operator makes a mistake and leaves mechanism un-attended for extended periods of time the plastic resin can degrade, clinging to the valve pin making it extremely difficult to remove. Having the valve pin housed in the actuator assembly, makes it near impossible to access the pin without destroying components.
This invention relates in general to improvements to valve gate actuators used in injection moldings systems. Although not limited to any particular field of use, the way the valve pin is accessed in present invention is particular useful when incorporated in runnerless injection molding systems.
For example U.S. Pat. No. 2007/0286923 to Jenko describes a unified monolithic piston and valve stem structure with reference to several other patents. This patent addresses reducing the number of parts in the actuator assembly, but doesn't allow easy access to the valve pin. If for instance, you wanted to remove one valve pin, you would need to remove the entire plate that houses all the valve pins in order to get to one pin. Another example U.S. Pat. No. 5,635,227 to Whisenhunt describes replaceable air cylinder unit and valve gate for injection molding machines. In this patent the valve gate actuator is disposed into top mold clamp plate and provides for access to the actuator assembly. Although this solution allows for access to individual actuators, it doesn't allow for independent removal of actuator and valve pin.
No other actuator assembly solution adequately address of ease of access to valve pin or actuator assembly.
It is therefore an object of the invention is to provide easy access to the valve pin contained in actuator assemblies on runnerless injection molding systems.
It is another object of the invention to provide easy access to hollow actuator shaft contained in actuator assembly on runnerless injection molding systems.
It is another object of the invention to provide a valve pin with removable head or clip
It is another object of the invention to provide an improved design for mounting the actuator assembly to the injection mold plate.
It is another object of the invention to provide easy access to valve pin mechanism by providing holes in back plate
It is another object of the invention to provide a means to detached valve pin from actuator assembly without disassembling actuator assembly or injection mold.